There has been concern about the treatment of deportees since the death earlier this month of Jimmy Mubenga, an Angolan failed asylum seeker who collapsed as he was being heavily restrained by G4S guards on a British Airways plane at Heathrow. After his death, fellow passengers who heard his cries for help said they regretted not having intervened.

Taylor was heading for a research trip in Africa with his friend Andrew Bowman, a PhD student, on 5 January. When they boarded the Virgin Atlantic plane, a man in a nearby seat, who was handcuffed to the seats and had security guards at either side and one leaning over the seats in front, was screaming.

"The passengers around me looked at each other in disbelief as they were confronted by the scene of this restrained man calling out for help," said Taylor. "Clearly the man was in considerable distress and pain."
He said the man screamed for several minutes as more passengers boarded the plane. "He was asking for his medication, with a minder telling him, 'You'll get your medication in Nairobi.' The man called out 'Help, help' repeatedly and shouted that he would kill himself in Kenya [if the deportation went ahead]."

Taylor said one of the G4S guards then leant over and pinned the man in his seat as other passengers became increasingly upset. Taylor went to approach the flight attendants but a guard told him to go back to his seat.

"I was immediately pushed in my back by one of the men that had been violently restraining the African man; he told me to sit down, keep quiet and that the African man was being deported, that these men were his escort or minders."

As the deportee continued to scream, Taylor decided he had to do something. "I was sitting there and decided I had to stand up for my values. I did not want to sit there for the next eight or nine hours feeling like I had sold out, like I had let this man down."

The pair demanded to see the captain but the request was initially refused. After the plane began to taxi the captain appeared and Taylor raised his concerns, but says they were dismissed.

"I was told by the cabin crew I could sit at the front of the plane so that I would not hear the man screaming. Which misses the point really."

The pair continued to voice their concerns before the captain ordered the plane to return to the terminal, where armed police were waiting for Taylor and Bowman.

"They were crowding around the exit and gave me the 'option' of leaving the plane – which I did. I had every privacy of mine invaded by the police, who analysed my passport, inquiring why I had visited countries such as Sri Lanka and UAE."

Taylor said he was questioned under anti-terrorism powers for several hours before the pair were escorted to the underground station at Heathrow, where "it was suggested" he get on a train to London.

Taylor said: "Witnessing the extreme distress of that man being violently restrained against his will and being detained myself was extremely distressing. Perhaps this shows what happens when passengers do voice concern over the treatment of a deportee, but I would do it again because what we went through is nothing compared to the trauma that poor man had to endure."

A spokeswoman for Virgin Atlantic said: "The safety and security of our passengers and crew is of paramount importance."

She added: "The Home Office makes the flight and security arrangements for all deportee passengers. It is not for the airline to refuse to carry a deportee passenger on the grounds of their immigration case as the airline has no knowledge of individual cases."

A spokesman for the UK Border Agency said it had not received any allegations of assault or criminal activity regarding the incident. He added: "The professional standards unit investigates all serious misconduct complaints from external sources and serious incidents concerning UK Border Agency staff or contractors. Where there is an allegation of assault or criminal activity the complaints are always referred to the relevant authorities, in this case the police."

G4S said its guards escorted the man but said they had received "no complaints or allegations regarding these individuals", adding that all complaints were taken seriously.

Senior officials from G4S will be questioned by MPs today when they appear before the home affairs select committee on Tuesday. The company said last week it was extremely disappointed to have lost a multimillion-pound contract to forcibly remove foreign nationals on behalf of the Home Office. The contract, which was up for renewal, has been given to a rival security firm, Reliance.